| 摘要 |
Aromatic esters of carbamic acid derivatives, e.g., p-chlorophenyl-N-methyl carbamate, are prepared by reaction of the corresponding aromatic alcohol, e.g., p-chlorophenol, and monoisocyanate, e.g., methyl isocyanate, in the presence of a catalytic amount of a combination of a 4-aminopyridine catalyst, e.g., 4-dimethylaminopyridine, and pyridine or methyl substituted pyridines. The product is substantially pure, having less than 0.80 weight percent allophanate ester by-product, e.g., p-chlorophenyl-N,N'-dimethyl allophanate, and less than 0.50 weight percent unreacted aromatic alcohol, e.g., p-chlorophenol. The reaction is readily controlled and characterized by the substantial absence of reflux. The product can be retained in the liquid state at reaction temperature for extended periods of time without significantly increasing the level of allophanate ester by-product.
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